An ethylene/tetrafluoroethylene copolymer (hereinafter referred to also as “ETFE”) is excellent in heat resistance, chemical resistance, weather resistance, gas barrier properties, etc. and is used in various fields including semiconductor industry, automobile industry, chemical industry, etc. Pelletized ETFE particles may be processed into various molded products by extrusion molding, injection molding, etc. Further, finer ETFE particles may be processed for coating or lining on the surface of a heat-resistant substrate by a powder coating method such as an electrostatic coating method, or a method such as a rotational molding method, and thus utilized for improvement in chemical resistance or protection of a metal surface of e.g. containers, tanks, pipings, joints, etc. Especially, coating by an electrostatic coating method is widely used, since it is thereby possible to easily form a coating film on the surface of an abnormally shaped article.
In general, as compared with a perfluorinated fluororesin such as a polytetrafluoroethylene resin, ETFE has good adhesion properties to a substrate, and therefore, in many cases, it is applied directly on a substrate surface after applying surface roughening treatment such as sand blasting to the substrate surface. However, in recent years, an ETFE-coated article has been required to be used in a severer environment, and it is desired to improve the adhesion properties between ETFE and the substrate.
Under these circumstances, a powder primer composition employing a reactive ETFE having reactive groups in ETFE molecules, is known (e.g. Patent Document 1). Further, a liquid primer composition employing a silane coupling agent in order to improve the adhesion properties between ETFE and a substrate, is known (e.g. Patent Document 2). Still further, an attempt to mix an epoxy resin powder to a fluororesin powder, followed by heat-treatment at from 180 to 200° C., is known (e.g. Patent Document 3).